The overall goal of this proposal is to develop a population-based registry of incident cases of insulin-dependent diabetes mellitus (IDDM) diagnosed under 18 years of age in the State of Colorado. The general purposes of the registry will be to 1) determine the descriptive epidemiology of IDDM in Colorado; 2) provide accurate baseline data against which potential case-clusters and outbreaks may be evaluated; 3) provide longitudinal follow-up on cases already identified to establish medical care utilization patterns and acute complications; 4) provide an unbiased source of patients from which to conduct etiologic and natural history studies; 5) identify patients at high risk of acute complications so that appropriate educational interventions might be planned. These purposes will be achieved through four principal activities; 1) case-ascertainment through a developing network of physicians, hospitals and lay persons will be continued, evaluated and streamlined; 2) Registry accuracy will be evaluated for completeness, over-reporting, and validity; 3) follow-up contacts will be established with eligible patients on an annual basis; and 4) data analysis will be conducted to describe IDDM in Colorado, and to test specified hypotheses.